Gallic acid-modified montmorillonite reinforced acrylic latex composite coatings: Enhanced mechanical and anticorrosion performances via barrier and interface passivation

To mitigate the global economic loss exceeding $1 trillion annually from corrosion, this study develops a multifunctional anti-corrosion composite coating by incorporating gallic acid-modified montmorillonite (D-MMT) into an acrylic latex (AL) matrix. The D-MMT, synthesized via ion-exchange, exhibited a significant expansion in interlayer spacing (from 1.270 nm to 1.680 nm) and enhanced dispersion within the polymer.At an optimal 4 wt% loading, the coating exhibited superior mechanical properties-increased hardness (from grade B to HB) and wear resistance-along with improved thermal stability (decomposition temperature elevated from 360 °C to 380 °C), attributed to hydrogen bonding between resin and nanofillers. Electrochemical analysis demonstrated exceptional corrosion protection, with low-frequency impedance modulus reaching 10⁸ Ω·cm² (two orders higher than pure AL) and corrosion current density reduced from 2.307 × 10⁻⁷ to 2.343 × 10⁻⁹ A/cm² after 35-day immersion in 3.5 wt% NaCl. XPS and FESEM-EDS analyses revealed a post-damage interface passivation protection mechanism via gallic acid-mediated chelation-reduction, forming a dense passivation layer that effectively blocked active corrosion sites, evidenced by enriched Fe²⁺ ions(58.3 %) and reduced iron content (29.9 % vs. 74.81 % in AL) at damaged regions due to the strong reducing and chelating capabilities of gallic acid. This work provides a scalable strategy for designing coatings with integrated barrier, mechanical, and self-healing functionalities for industrial applications.